GRB 070429B
GCN Circular 7145
Subject
GRB 070429B: Possible UVOT Detection of an Optical Afterglow
Date
2007-12-10T15:32:47Z (18 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <sholland@milkyway.gsfc.nasa.gov>
Holland, S. T. (CRESST/USRA/GSFC), de Pasquale, M. (UCL/MSSL), and
Markwardt, C.~B. (CRESST/GSFC/UMD) report on behalf of the Swift/UVOT
team:
The Swift/UVOT observed the field of the short-hard GRB 070429B
starting 230 s after the BAT trigger (Markwardt, et al., GCN
Circ. 6358). We have re-examined this data in light of the redshift
for the Antonelli, et al. (GCN Circ. 6372) source "A" reported by
Perley, et al. (GCN Circ. 7140). We find weak evidence in the UVOT
data for a fading source located inside the refined XRT error circle
(Beardmore, et al., GCN Circ. 6360) at
RA = 21:52:03.68 (J2000)
Dec = -38:49:43.6 (J2000)
with an uncertainty of 0.6 arcsec (90% confidence). This is 0.6
arcsec from the ground-based position of source "A". For a redshift
of z = 0.904, and (H_0,Omega_M,Omega_Lambda) = (70,0.3,0.7) this
corresponds to 4.7 proper kpc. This possible source is detected with
a 3.9-sigma significance in a summed image (summed over all seven
filters) between 591 and 2661 s after the BAT trigger. It is not
detected in subsequent all-filter summed images. This possible UVOT
source has the following magnitudes and upper limits. All magnitudes
are on the UVOT system described in Poole, et al. (2007, MNRAS, in
press).
Filter T_start T_stop Exposure Mag Err Significance
v 2002 2661 94 19.3 0.4 2.5
6805 7004 393 >20.1 3-sigma upper limit
b 1460 2598 156 20.5 0.5 2.2
34,978 35,884 885 >22.0 3-sigma upper limit
u 403 42,285 2260 >21.8 3-sigma upper limit
uvw1 379 41,789 3075 >22.4 3-sigma upper limit
uvm2 354 20,226 2192 >22.0 3-sigma upper limit
uvw2 456 30,222 2378 >22.4 3-sigma upper limit
white 591 977 117 21.6 0.5 2.2
6395 8027 393 >22.1 3-sigma upper limit
The observations where the suspected source is weakly detected
are all at less than one hour after the BAT trigger. The earliest
reported ground-based detection of source "A" is Cucchiara, et
al. (GCN Circ. 6368) who find r = 23.18 +/- 0.15 at approximately 4
hours. Perley, et al. (GCN Circ. 7140) find R = 23.24 +/- 0.05 at
approximately 7 months, which implies that the source did not fade,
and conclude that the "A" source is the host galaxy. They also find g
= 24.29 +/- 0.14 at this time. If we assume that the SDSS g band is
approximately similar to the UVOT v band then the expected v magnitude
of the host at 2332 s (assuming a constant magnitude) is v ~= 24.3,
which is 5 mag fainter than the UVOT detection at that time. This
corresponds to a mean decay index of alpha ~= -2.5.
The observed decay power-law indices from the UVOT data are
alpha_v <= -0.6 +/- 0.3, alpha_b <= -0.5 +/- 0.2, and alpha_white <=
-0.2 +/- 0.2. The shallow decay slope in the white filter, and the
faintness of the White detection at early time (t_mid = 784 s)
relative to the b and v detections at later times (t_mid = 2332 (v),
2029 (b)) suggest that the afterglow candidate may have increased in
luminosity at some point between approximately 784 and 2029 s.
We do not detect any source at the position of source "B"
(Antonelli, et al., GCN Circ. 6372) down to the following limiting
magnitudes.
Filter T_start T_stop Exposure 3-Sigma Upper Limit
v 230 31,793 2011 >21.5
b 427 35,115 1463 >22.3
u 403 42,285 2260 >21.9
uvw1 379 41,789 3075 >22.4
uvm2 354 20,226 2192 >22.0
uvw2 456 30,222 2378 >22.4
white 247 36,269 1088 >22.7
The values quoted above are not corrected for the expected
Galactic extinction corresponding to a reddening of E_{B-V} = 0.03 mag
(Schlegel, et al. 1998).
GCN Circular 7140
Subject
GRB 070429B: Probable host galaxy and redshift
Date
2007-11-30T23:25:17Z (18 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley, J. S. Bloom, M. Modjaz, D. Poznanski (UC Berkeley) and C.
C. Thoene (DARK) report:
On the night of 2007-07-18 we re-observed the field of GRB 070429B (GCN
6358, Markwardt et al.), likely to be a short-hard burst (T90 = 0.5 +-
0.1 s, GCN 6365, Tueller et al.) under photometric conditions using the
Keck I telescope + LRIS, in g and R filters simultaneously for a total
integration of 930s(g) / 840s(R) under relatively poor seeing. We
further imaged the field using GMOS on Gemini-South on 2007-11-27 for
1200s in r filter under excellent seeing.
The bright source reported by Cucchiara et al. (GCN 6368), designated
object "A" by Antonelli et al. (GCN 6372) and likely the host galaxy of
the GRB, is well-detected in R and r and weakly detected in g. Using
Landolt standard stars we measure an aperture magnitude for this object
(in a 2.1" radius aperture) of
g = 24.79 +/- 0.14
R = 23.24 +/- 0.05
This is consistent within errors with the magnitudes reported by
Cucchiara et al. and Antonelli et al. 4 and 5 hours after the burst,
respectively. Image subtraction of the new Gemini imaging versus the
earlier epoch (GCN 6368) reveals no variability to a limiting magnitude
of R > 24.5, ruling out an afterglow contribution in the first epoch
(4.84 hours after the burst) at this level.
Object "B" is also detected in both filters, and also shows no evidence
for variability.
On the night of 2007-10-09 we performed longslit spectroscopy covering
both targets ("A" and "B") in two integrations of 1500s each, using Keck
I + LRIS.
The trace of object "A" is faint and the spectrum is mostly featureless,
but a faint line signature is observed centered at 7098 Angstroms, with
a FWHM of 6 Angstroms. The feature appears present in both exposures,
though this site is severely affected by a cosmic ray in one exposure.
We identify this feature as most likely being the [OII]3727 doublet.
Other line identifications (H-alpha, H-beta, or [OIII]) are disfavored
due to the absence of corroborating lines that would be expected over
our spectral range (3500-8900 Angstroms) in those cases.
Association of this feature with [OII] indicates a redshift for this
object of z=0.904. Calibrating relative to R-band photometry, we
estimate a preliminary line flux of 3e-17 erg/s/cm^2, corresponding to
an unextincted star formation rate (Kewley et al. 2002) of 0.7 M_sun/yr,
comparable to that observed in previous short burst hosts. We note also
the red color of this galaxy.
No obvious trace or line features are observed for object B.
GCN Circular 6604
Subject
GRB 070429B: NIR Observations
Date
2007-07-06T23:23:50Z (18 years ago)
From
Melissa Nysewander at STScI <mnysewan@stsci.edu>
M. Nysewander, A. Fruchter and J. Graham (STScI) report on behalf of a
larger collaboration:
We observed the entire BAT error circle of the short GRB 070429B
(Markwardt et al. GCN 6358) with ISPI on the Blanco 4-m at CTIO at a
mean time of 06:10:28 UT on April 30, 2007 (1.13 days post burst) in 18
x 60-s J-band exposures, and again at a mean time of 06:23:04 UT on June
2, 2007, (34.2 days post burst) with the same exposure sequence.
Due to the questionable nature of the faint XRT afterglow candidate
(Beardmore et al. GCN 6360), we searched the entire BAT error circle by
subtracting the two epochs using ISIS2 (Alard, 2000). We do not find any
variation between the two epochs to the limiting magnitude of the first
epoch, J ~ 21.5. Specifically, the source within the XRT error circle
noted by Cucchiara et al. (GCN 6368) also did not vary between the two
epochs.
GCN Circular 6372
Subject
GRB070429B: VLT observations
Date
2007-05-01T21:57:49Z (19 years ago)
From
Angelo Antonelli at Obs. Astro. di Roma <a.antonelli@oa-roma.inaf.it>
L.A. Antonelli (INAF-OAR & ASDC), L. Stella (INAF-OAR), G. Tagliaferri (INAF-
OABr), E. Jehin, L. Schmidtobreick (ESO),report on behalf of the MISTICI
collaboration:
We observed the refined XRT error circle of the short burst GRB 070429B
(Beardmore et al, GCN 6360) with VLT-UT1 (Antu) and FORS2 in two different
epochs. Images were taken in both the R and B bands starting on Apr. 29 at 09:
26:00 (about 5.5 hr after the burst) for a total exposure time of 900 sec in R
band and 600 sec in B band. Another image of the field was taken in the R band
only starting on Apr. 30 at 09:10:56 UT (about 29.5 hr after the burst) for a
total exposure time of 1800 sec under better seeing conditions.
At both epochs we found two objects within the XRT error circle:
Object A is located well within the XRT error circle at:
RA = 21:52:03.7
DEC = -38:49:42.9
Object B is located close to the border of the XRT error
circle at:
RA = 21:52:03.4
DEC = -38:49:43.1
Coordinates are J2000 and with an error of 0.2".
Object A was detected in R band at both epochs with good S/N. It appears to be
extended and consistent with the revised position of the object observed by
Cucchiara et al (GCN 6370); its R magnitude is 23.2 +- 0.2, calibrated by
using the USNO B1 catalogue. Object A was only marginally detected in the B
band. Object B was marginally detected in the first R band observation, with a
better detection during the second night at a R mag of 24.6+-0.3. Also object
B seems extended.
We find no evidence of a fading behaviour in either objects. Most likely one
of them represents the host galaxy of GRB070429B.
We thank the ESO Paranal staff for their excellent support.
This message can be cited.
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GCN Circular 6370
Subject
GRB070429B: position correction
Date
2007-04-30T21:20:31Z (19 years ago)
From
Antonino Cucchiara at PSU <cucchiara@astro.psu.edu>
Cucchiara A. (PSU), S. B. Cenko (Caltech), D. B. Fox (PSU), E. Berger
(Carnegie), and J. S. Bloom (UC-Berkeley) report on behalf of a larger
collaboration:
We re-analyzed our GMOS imaging data on GRB070429B (Cucchiara et al.,
GCN 6368). We found the position previously reported for the sole
object in the XRT error circle was incorrect. An updated position for
this object is:
RA = 21:52:03.729 (J2000)
DEC = -38:49:42.84 (J2000)
This represents an offset of 2.70" W and 0.05" S from our previously
reported location. The new position was calculated with respect to
several USNO-B1 objects in the field. We estimate a positional
uncertainty of 0.3" in each coordinate.
We apologize for any inconvenience this may have caused.
GCN Circular 6368
Subject
GRB070429B: possible host galaxy detection
Date
2007-04-30T01:16:44Z (19 years ago)
From
Antonino Cucchiara at PSU <cucchiara@astro.psu.edu>
Cucchiara A. (PSU), D. B. Fox, S. B. Cenko, E. Berger:
We observed the refined XRT error circle of GRB 070429B (GCN 6360) with
GMOS on
the Gemini-South telescope for a total of 900 sec in r-band starting on
2007 April 29 at 07:59:55 UT (~ 4 hr after the burst). Within the XRT
error circle we
find a single faint object located at:
RA = 21:52:03.96 (J2000)
DEC = -38:49:42.79 (J2000)
The object appears to be extended and we cannot determine a possible
fading at the moment. The r magnitude is 23.18 +- 0.15 calibrated using
four stars from USNOB1 catalogue.
We thank the Gemini-South staff for their support.
GCN Circular 6367
Subject
VLA observation of GRB 070429B
Date
2007-04-29T20:21:27Z (19 years ago)
From
Poonam Chandra at U Virginia/NRAO <pc8s@virginia.edu>
Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on
behalf of the Caltech-NRAO-Carnegie GRB Collaboration:
"We used the Very Large Array to observe the field of view toward a
short burst GRB 070429B (GCN 6358) at a frequency of 8.46 GHz on
2007 April 29th at 15.73 UT. The GRB is undetected and the peak radio
flux at the SWIFT-XRT position (GCN 6360) is 04+/-100 uJy.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 6366
Subject
Swift/UVOT observations of GRB070429B
Date
2007-04-29T17:03:42Z (19 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
P. Schady (MSSL/PSU) and C. Markwardt (GSFC/UMD) report on behalf of the
Swift UVOT team:
Swift/UVOT observed the field of GRB 070429B starting 297s after the BAT
trigger. No new source is detected either within the refined XRT position
(GCN 6360) in any of the UVOT filters, in either single or co-added
exposures. The 3-sigma upper limits for the co-added exposures in each
filter are as follows:
Filter T_mid(s) Exp.(s) Mag 3-sig UL
White 1009 302 19.68
V 1489 605 19.64
B 1812 184 19.83
U 2092 392 19.80
UVW1 1625 253 19.31
UVM2 1601 253 19.48
UVW2 1682 214 19.63
where T_mid is the weighted mid time of the co-added images. The reported
upper limits are uncorrected for the estimated Galactic reddening of
E(B-V) = 0.03 mag.
GCN Circular 6365
Subject
GRB 070429B, Swift-BAT refined analysis
Date
2007-04-29T16:37:10Z (19 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU)
on behalf of the Swift-BAT team:
Using the data set from T-240 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070429 (trigger #277582)
(Markwardt, et al., GCN Circ. 6358). The BAT ground-calculated position is
RA, Dec = 328.006, -38.857 deg which is
RA(J2000) = 21h 52m 1.4s
Dec(J2000) = -38d 51' 24.8"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 66%.
The mask-weighted lightcurve shows 3 or 4 overlapping peaks starting at
~T-0.2s sec and ending at ~T+0.5 sec. T90 (15-350 keV) is 0.5 +- 0.1 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.2 to T+0.3 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.71 +- 0.23. The fluence in the 15-150 keV band is 6.3 +- 1.0 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.45 sec in the 15-150 keV band
is 1.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
GCN Circular 6360
Subject
GRB 070429B: Swift XRT refined analysis
Date
2007-04-29T13:19:19Z (19 years ago)
From
Andy Beardmore at U Leicester <apb@star.le.ac.uk>
A.P. Beardmore, K.L. Page, P.A. Evans, R.L.C. Starling (U. of Leicester),
C. Guidorzi (INAF-OAB, Univ. Bicocca), and C. Markwardt (GSFC/UMD) report
on behalf of the Swift XRT team :
We have analysed the first three orbits of Swift XRT data from
GRB 070429B (trigger number 277582, Markwardt et al. GCN circular
6358), which has a total photon counting mode exposure of 5.8ks. Due
to a delayed slew because of an Earth-limb constraint, the XRT arrived
on the source 244s after the BAT trigger. The tentative X-ray source
identified in GCN 6358 is clearly detected in the first orbit of data,
and is absent thereafter. The refined XRT position from 2.4ks of data
in the first orbit is
RA, DEC (J2000) = 328.0159, -38.8284
which is
RA(J2000) = 21d 52m 03.82s
DEC(J2000) = -38d 49' 42.2"
with an uncertainty of 5.1 arcsec (radius, 90% containment).
This is 61 arcsec from the inital BAT position and 6.2 arcsec
from the initial X-ray position reported in GCN 6358.
An XRT light curve created from the first orbit of data, binned with
a minimum of 10 counts/bin, reveals a decaying source. A powerlaw
fit yields a poorly constrained decay slope of 0.94+/-0.47.
The X-ray spectrum from the first orbit (covering 254 to 2691 seconds
after the BAT trigger), modelled with an absorbed powerlaw and fit
using Cash statistics, gives a photon index of 2.5+1.3-1.2. An upper
limit of 5.9e21 cm^-2 on the column density was found, compared with
the Galactic value of 1.8E+20 cm^-2 in this direction. The absorbed
(unabsorbed) 0.3-10.0keV flux for this spectrum was 5.9E-13 (1.1E-12)
ergs cm^-2 s^-1.
Assuming the source continues to decay at the same rate, we predict an
XRT count rate of 3.0e-4 count/s at T+24 hours, which corresponds to an
observed (unabsorbed) flux of 1.5E-14 (2.8E-14) ergs cm^-2 s^-1.
This circular is an official product of the Swift XRT team.
GCN Circular 6359
Subject
GRB 070429B: ROTSE-III Optical Limits
Date
2007-04-29T03:56:35Z (19 years ago)
From
Brad Schaefer at LSU <schaefer@grb.phys.lsu.edu>
B. E. Schaefer (Louisiana State), W. Rujopakarn (U Mich), E.S. Rykoff (U
Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to the short-burst GRB 070429B (Swift trigger 277582; Markwardt
et al. GCN 6358), producing images beginning 7.9 s after the GCN notice
time. An automated response took the first image at 03:09:30.9 UT, 26.5 s
after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec
20 60-sec exposures, and observations are continuing. These unfiltered
images are calibrated relative to USNO A2.0 (R).
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma BAT error circle and within the error circle for the possible XRT
source, for both single images and coadding into sets of 10; the field is
not crowded. Individual images have limiting magnitudes ranging from
15.5-17.5; we set the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
03:09:30.9 03:09:35.9 5 15.5 26.5 N
03:09:30.8 03:10:56.5 85 17.3 26.4 Y
03:27:43.5 03:39:11.4 687 18.5 1119.1 Y
GCN Circular 6358
Subject
GRB 070429B: Swift detection of a short burst
Date
2007-04-29T03:41:59Z (19 years ago)
From
Craig Markwardt at NASA/GSFC/UMD <craigm@milkyway.gsfc.nasa.gov>
C. B. Markwardt (GSFC/UMD), L. M. Barbier (NASA/GSFC),
S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester),
J. K. Cannizzo (NASA/UMBC), M. M. Chester (PSU),
N. Gehrels (NASA/GSFC), S. D. Hunsberger (PSU),
W. B. Landsman (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), G. Sato (GSFC/ISAS) and
R. L. C. Starling (U Leicester) report on behalf of the Swift Team:
At 03:09:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070429B (trigger=277582). Swift slewed to the burst
following a 165 second delay due to the Earth-limb constraint.
The BAT on-board calculated location is
RA, Dec 328.024, -38.844 which is
RA(J2000) = 21h 52m 06s
Dec(J2000) = -38d 50' 37"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a short spike
with a duration of about 700 msec. The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
No source was automatically found onboard by the XRT; however, 213s of
downlinked data suggest there is a possible source at RA, DEC
(degrees) = 328.01551, -38.82670 which is
RA(J2000) = 21h 52m 03.7s
Dec(J2000)= -38d 49' 36.1"
with an uncertainty of 9.1 arcsec (90% containment).
UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 247 seconds after the BAT trigger. No
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image covers 25% of the BAT error circle, and fully
covers the possible XRT position. The typical 3-sigma upper limit has
been about 18.5 mag. The 8'x8' region for the list of sources
generated on-board covers 100% of the BAT error circle. The list of
sources is typically complete to about 18 mag. No correction has been
made for reddening of E(B-V)=0.026.